1. Field of the Invention
The invention relates to a metallic catalyst carrier foil, especially formed of steel resistant to corrosion and/or to high temperatures, to be coated with ceramic catalytic material, and a method of manufacturing the same.
2. Description of the Related Art
Such thin metallic foils are preferably used as smooth or corrugated layers in the manufacture of catalyst carrier bodies. In general, such foils are first aligned to form a catalyst carrier body, which is a so-called matrix with honeycomb-like canals and the foils are subsequently coated. It is also known to apply the coating prior to winding-up or stacking the individual layers.
The actual coating with catalytic material represents an important and difficult step during the manufacture of catalysts. Since metal oxides and other ceramic materials are frequently used as catalysts, the carrier sheets must exhibit special properties so that good adherence of the coating is obtained.
German published, non-prosecuted application DE-OS No. 28 53 023 describes various metal foils which are suitable for coating. From this publication it is known that the adhesion of the coating is improved by suitable perforation, because bridges are formed between the layers coating both sides of the foil through the perforations. This publication only describes macroscopic holes with dimensions on the order of 1 mm which are produced by costly methods and are too large for optimum adherence of the coating.
Similarly, U.S. Pat. No. 4,006,105 discloses a catalyst in which a foil is slotted and processes into metal mesh with macroscopic holes. Netherlands patent No. 68 13 245 provides a method of drilling very small holes in a foil, but that method is not very economical since the foil must first be produced and then drilled.
It is furthermore mentioned in German published, non-prosecuted application DE-OS No. 22 26 662 that catalyst carrier foils can be formed by electroplated deposition of desired alloying components. In this connection, the possibility is also mentioned to make expanded metal from such foils which has macroscopic diamond-shaped holes. Carrier foils constructed in this manner also do not prevent individual parts of the coating from crumbling away.